By casting this spell, the priest causes a magical thorny vine to appear and wrap itself around a chosen creature. A successful saving throw means the attack is foiled, and the vine dissipates harmlessly. Failure results in 1d4 points of damage, plus a number of additional points of damage equal to the Armor Class of the creature. Thus, a human in plate mail (AC 3) takes 1d4+3 points of damage. In addition, the creature is bound and cannot take any other actions until it escapes.
To escape the bonds, a creature must make a successful saving throw vs. spell at -4. The creature takes another 1d4 + AC points of damage for every escape attempt, regardless of success. Exceptionally large and powerful creatures can snap the vine easily. Otherwise, the caster can, by concentrating for a full round and squeezing, cause the vine to constrict and inflict damage (as above), or can dismiss the thorns of binding with a gesture.
Notes: Uncommon for priests of the Dark Sun setting.